I am using U Mobile prepaid for my iPad. Not too bad.

Was using Digi Discovery Day but was not too happy with their speeds (generally just shy of 1Mbps, ping 200-300ms, though it feels especially slow when loading youtube videos) and the fact that it is nearly unusable from 7pm-7am (the "off-peak" hours)

For U Mobile, I am getting speeds of upto 4Mbps (DL) 1.5Mbps (UL), but most of the time, ping is quite bad. So far, the worst ping I have recorded is 5000+ ms O_o. Though usually its in the region of 1000ms +/- (still quite bad). But for normal browsing, watching youtube videos, feels faster than Digi.