Whether the blocks in the big Revell kits are "good enough" really depends, like most such things, on the standards of the individual modeler. They certainly work, and they look more like real blocks than the ones in most other companies' kits. Whether they need to be drilled out or not probably will depend on the age of the kit you get; in any case, the drilling process only takes a few seconds.
In terms of accuracy, they have two problems: they aren't configured like most blocks on a real ship, and there aren't enough different sizes of them.
The typical eighteenth-century block consisted of a wood shell with a very hard wood (traditionally lignum vitae) sheave inside, held in place by a lignum vitae pin. (Lignum vitae contains a high percentage of oil, which functions as a lubricant for the sheave.) It had a groove around its exterior. A piece of rope ran in the groove. That rope might be a piece of rigging itself, or it might be a short piece, called a strop, with one or two eyes worked into it. (Eighteenth-century blocks were, with few exceptions, rope-stropped blocks. Metal stropped blocks came later.)
The problem for plastic kit manufacturers is that a rigid, two-piece mold (such as is normally used for producing injection-molded plastic parts) is physically incapable of producing a part with a hole through it and a groove around it. (Think about it. Such a part wouldn't come loose from the mold.) The geniuses at Imai, back in the late seventies, did come up with a system for making beautiful, accurately-shaped blocks and deadeyes using the "slide-molding" technique, but Revell and Heller never did. So they compromised.
The typical Revell block, if carefully painted, can be made to look convincingly like a rope-stropped block - though the eye will be a bit on the big side. For the Constitution kit, the modeler may quite reasonably conclude that the kit blocks are plenty good enough. (The other two big Revell kits, the Cutty Sark and the Kearsarge, are another matter. They really ought to have, for the most part, metal-stropped blocks.) There remains, however, the problem of the number of sizes.
The Constitution kit contains single and double blocks in two sizes. An actual full-rigged ship had at least a dozen, and probably more. That includes all the ship's rigging - much of which the typical modeler may not want to include. (I certainly wouldn't recommend trying to include every line in a first project.) The smaller size in the kit is pretty big for many of the lines in a model on that scale (1/8" = 1'). I don't have the kit in front of me, but if I remember correctly the small blocks are somewhat more than 1/8" long (including the strops). A foot-long block is a pretty big one. Trying to reproduce the huge variety of block sizes in a model would be overkill, but having more than two sizes will greatly improve the appearance of the finished product.
Various manufacturers offer aftermarket blocks. The wood ones sold by Model Expo aren't bad; the wood ones from The Lumberyard are better. My personal favorite, though, is the line of cast Britannia metal blocks from Bluejacket (www.bluejacketinc.com). They're properly proportioned for most purposes, and they come in lots of sizes - the smallest of which (nominally 3/32") is just about right for most of the lighter lines of a 1/8" = 1' scale frigate. They do require some effort; the sheave holes frequently have to be reamed out, and the grooves for the rope strops (Britannia metal can be cast in flexible rubber molds, so it's possible for these blocks to have both holes and grooves) need to be cleaned up with a file. And, of course, they have to be painted. (An alternative, if you can justify black blocks, is to dip them in a chemical called "Pewter Black," which Bluejacket also sells.)
Britannia metal isn't cheap, and a full outfit of blocks for a model like the Constitution will cost quite a bit. There is, however, no reason on earth to order the whole complement of blocks at the same time. My custom is to order as many I'll need in two or three weeks, and order another batch when my stock starts getting low. (Another benefit of that approach: it's considerably less intimidating than confronting forty or fifty dozen tiny little blocks at the same time.)
It is, of course, up to the individual modeler to choose the route he/she wants to go - in this regard as in all others. I would, however, suggest that if you're going to replace the kit blocks, you should also consider the deadeyes. The model's appearance will be tremendously improved if the plastic contraptions in the kit, with their molded plastic lanyards, are replaced with genuine, individual deadeyes rigged with thread lanyards. Unfortunately, though, setting up deadeyes and lanyards is one of the trickier parts of rigging a sailing ship model. And, by definition, it has to be done early in the rigging process, before the builder has much opportunity to practice on simpler jobs. And an eighteenth-century warship has an awful lot of deadeyes.
If you do decide to go that route, I can enthusiastically recommend Bluejacket metal deadeyes. But I do suggest giving the whole matter a good deal of thought. It's a depressing fact of the hobby that most sailing ship models never get finished - especially those started by newcomers. A bit reason for that state of affairs is that rigging, especially in the case of a big, full-rigged ship, takes so much time and involves so much repetition. A reasonably thorough rigging job on a Constitution with aftermarket fittings will require about two hundred deadeyes and close to a thousand blocks (depending, of course, on how much of the running rigging the modeler decides to include). I don't blame anybody who decides that Revell's simplified approach isn't such a bad idea.
Hope that helps a little. Good luck.