Another company makes a product called the Amigo which is more or less an iPaq with a type 2 PCMCIA slot built it. It is the same price as the iPaq and even sports a StrongARM @ 206mhz.
My vote is for the Casio E125, but I am biased because I already own one.
The only problems I have with the iPaq are:
1. Display. Side lit instead of backlit. E125's display is easier to read because it is back lit.
2. Expansion costs $$$. It does not come with a Compact Flash or PCMCIA adapter - you have to buy it's expansion via sleeves.
3. Stylus problems. The stylus on just about every iPaq I have seen has a problem staying in the unit.
4. Lack of back up battery. If your battery on your iPaq goes out, you are screwed. But, E125 has a backup battery. I know that a simple work around is to simply charge it, but people's lives should not have to revolve around charging their PDAs. A MS rep I talked to at CES told me to think of your PDA the same way you think of your cell phone and you will be fine. This is an unfortunate negative aspect that Palms do not have a problem with.
5. Low availability. We are not talking about uptime, but the fact that so far, I have had a huge problem trying to purchase one of these. Because I had such a tough time finding an iPaq, I went out and bought a Casio E125. I do not regret this purchase at all due to aforementioned issues I have with the iPaq.
6. Slipperiness of the iPaq. This is a weak complaint, but without a sleeve, the iPaq could easily slip out of your hand. I don't think anyone wants to drop their 500$ investment.
Cool things about the iPaq:
1. Expandability. The ability to add sleeves is a great feature. I like the ability to add PCMCIA modems, 802.11 adapters, 100baseTX ethernet adapters, etc.
2. Cool software. Doom and Quake have both been ported to the iPaq. Of course, the playability is pretty lame since the buttons on the iPaq are too small.
3. Speed of the CPU. The 206mhz is by far the fastest CPU in a WinCE based PDA to date. If you must have the fastest (and it is overclockable via a software hack/patch), the iPaq is probably for you.
I vote for the
Casio E125.
One last word about the iPaq vs. Cassiopeia E125: The iPaq can only display 4096 colors while the E125 can display 65,536. More colors, in my opinion, is better.