Hi Andrew,
I order from them quite frequently and rarely have any issues.
There's really only one "gotcha". This is, only order items which have the green "In Stock" status. Anything with the blue "Available" status means they don't have it in stock, but it may be available from their supplier. There are a lot of long OOP items listed as "Available" so beware.
If ordering multiple items, un-tick the option (I can't recall the exact wording) to ship all items together. This will make sure they ship what they can, rather than wait for an item which might go out of stock between the time you place your order and the time when they pack the order.
Another possible issue is that they charge you up front when you place the order, not when they ship it,. This hasn't been a problem for me so far.