Yup, Windows phone 7 is definitely refreshing. Its butter smooth.. But it has some serious limitations which may be good for some and con for others. So carefully consider them before buying. I am listing them here for your reference.
1. WP7 doesn't support Bluetooth file transfer. So if you are of the kind who receive lots of files from your friend, this will be a serious limitation.
2. WP7 doesn't support USB mass storage. Means, you will need Zune software to transfer everything to your phone. If you want to connect your phone to a PC, you need to install Zune in that PC. So if you are that kind of person, who connects your phone to friends comp and takes files, you will have to install Zune in every PC.
3. Zune supports very very limited kind of Formats. Currently only these files are recognized by zune.
Music - .mp3 .m4a .wma
Video - .mp4 .wmv
Photos - .jpeg
So, you cannot sideload any other file to your phone. No, not even .doc, .pdf files. Also, if the video file is in .avi .mkv .vob or any other format, Zune will convert it into .mp4 while uploading. So it may take much more time if you are a videophile.
4. There is one workaround to store files in your phone. You can upload into your mail and from phone You can download them and check .pdf .doc etc. But this will require a good internet connection on your phone or wifi network.
5. Main features of WP7 are live tiles, tight integration with Facebook, Twitter, LinkedIn etc. All the major features which differentiate it from android need good internet connection.
So see if you can live with these limitations. If so, WP7 will be great for you. And I suggest you to buy Omnia W instead of Lumia 710. Omnia W has better screen and Lumia 710's music is horrible according to GSMArena which does scientific tests and always gives great reviews of phones. Check audio quality section in the below link.
http://www.gsmarena.com/nokia_lumia_710-review-708p5.php