Yes, personally I think it is very slow. Coming from an iPhone 3G, I never used the wall charger, only ever had it plugged into my laptop. I could be at 20% and plug it in for half an hour and be over 50 again, and a full charge in a couple hours. Having the Incredible plugged in to the same laptop for a couple hours yesterday (charge only) and it gave me maybe 10-15% back.
I tried one thing yesterday, plugged it into my laptop then turned the phone completely off briefly. During that time it seemed to charge much faster...so it seems that the charging by USB doesn't offset the battery drain very much.