"MiTAC has recently launched two totally different pocket devices. While the lower model Mio339 is intended primarily for the down-market and the young generation (and its review was not very positive), MiTAC Mio558 is designed for discerning customers who will appreciate all the various communication options and two expansion slots. Today, we are going to examine the latter model."

PDAgold calls this a big review; perhaps they were inspired by
my i700 review 
In any case, they have done a fantastic job, with lots of comparison photos, screenshots, and benchmarks, so if you've had your eye on this Pocket PC, you should definitely take a look first.