I have earlier used O2(Windows), sony P91i (UIQ 3.0- touch), nokia E61i(symbian 3rd) and tried this E90 for 3months. Now I have switched to Samsung i780(windows).
Pros:
Good battery life even with big screen
Good voice and signal clearity
many features.. gps, 3.5 camera, FM, music, Mail of Exchange, card slot.(only upto 2gb)
Wide screen.
Cons
Inside Keyboard not usable. Keys are too far and you cant press extreme keys. Also keys too hard. you cant press it unless you put extra efforts. It pains. Shortcut keys are not properly maped and customizable. Keyboard is not used for proper adventage. Keys touch the screen. So screen is damaged in 3-4monts of usage. you will see lines on the screen.
Inside Four way navigation key on inside keyboard is almost flat. So you cant press the edge to go different ways. It leads to many accidental press of wrong navigation.
Outside keys (accept , reject) has bevel edge. They cant be press as they pierce the thumb flesh and then when you apply pressure , two other keys next to it get pressed. Bad design of front keys.
The outside plastic body is fragile at the rear. When you tend to open the inside keyboard, you have to press hard at the two edges and many times the rear plastic cover on the battery gets opened.
They camera key is very strange. Its not vertical press, but a povit key. So the key swings and the experience of camera click is not there.
The mail for Exchange: I dont understand why there was so hype of this phone as an emailing phone. Its a pathetic emailing tool. The mail for exchange is like a primitive telnet/dos based application. It lacks many mail features those are in windows mobile. It doesnt have search mails. There is not spell check. there is not sort by date, sender, subject. There is no email suggester(if you type first few words in To field, automatically windows mobile shows matching emails). IT doesnt support imap folders. All sent items from exchange or from pop mail are stored together in sent folder of phone(Strange). The calender application has limitations.
Too bulky. ITs like holding a brick. You can use this tool for self defence. Bang on someones head. Your wrist will start paining if you hold this phone in single hand for long time.
GPS is only 3 months free. IT asks for Rs.4000 per year for GPS. Instead go and buy Satguide or mapmyindia gps software and map for Windows mobile for Rs1000, unlimited usage.
Too costly phone. Rs35000 ($875). ITs just a style and not a value for money.
Redail button(Green key), is not properly mapped to all calls. So if Person-A calls you and you had called previously to Person - B, and try to press this redial button assuming that the last call was from "A" and it will dial him. but instead..... it will dial person "B".... I have lost money by redialling to wrong people.
I have now switched to samsung i780. Wait for my review. Is sleek, touch screen, windows mobile, and qwert key pad.
cheers