I've had an HTC desire for 8 months. I'm also an engineer, and we're designing products powered by Android. As a former professional programmer I have a low tolerance for crappy SW, so I'm astounded that the gMail App on my phone is so terribly incomplete.
Here's the situation: I can see e-my mails ... as long as I don't want to see anything newer than about 1 month old.
I have auto-sync on.
I try manually syncing on the 3g wireless network ... icons blink for a while, but it doesn't pull down any newer messages.
I try manually syncing on Wifi ... same result.
If I SEARCH on the sender or subject to try to retrieve a newer e-mail, it will show the newest e-mails in the search results.
But if I try to load any of those messages it fails.

I can get at newer messages using the web-interface, but it is SO slow, and often fails.
I have 2 accounts: personal and a work acc't with Google APPs.
Personal is 20% full, (of 7.6 Gigs storage)
Work is 79% full "Using 6492 MB of your 7618 MB"
I get 200 - 300 legit e-mails/day @ work, not counting spam.

Accessing only mail that is 3+ weeks old is useless.
So I can't travel without a laptop for e-mail, which sucks.
But its not that it won't access today's e-mail ... it will ... in 3 or 4 weeks time!! ????
Any ideas?