I've been a Transformerland customer for a very long time and for most of those years, I too had nothing but positive things to say of him.
In recent months though he's been nothing but trouble. He forgot to ship certain items with my orders, failed to give accurate descriptions and takes weeks to reply to emails.
My last four orders with him have been terrible from a customer service point of view. He still owes me $25, a replacement G1 Omega Supreme tank, a new complete Gnaw and another Blaster figure - all of which were either badly yellowed or broken. I've given up chasing this stuff owed to me. He just doesn't bother to reply with the same urgency or care that he used to.
Again - I'd like to reiterate the fact that I was once a very, very happy customer of his and have even spent a small fortune at transformerland but after these terrible experiences, I really do want to discourage others from buying from him. I tried so very hard to be reasonable and work with him on rectifying my order issues, but he's become a joke really.
Three other
very important eye openers for me as well (from a customer point of view) pointed out to me by a fellow American collector;
1. Matt gives virtually everything in his inventory a C8-C9 rating, when half the time this is not the case
2. His inventory is larger than other G1 specialised stores, but everything he has in stock can easily be bought from ebay
3. He charges more than the ebay marketprice. This is the critical point that most people fail to notice (... I did

) $15US for a loose beachcomber, $45US for a loose astrotrain, $70US for Thundercracker - Even if you negotiate the prices for these, you can still buy them cheaper on ebay
Anyway, that's my two cents.