Some apps i used all the time and found them essential in my ipad were:
Dropbox, Pocket (former read it later), pulse, AutocadWS, nba.tv (international league pass) and maybe Photoshop express and some other i dont remember now.
Dropbox: seems they didnt want to release an official app for wp7. there are some good 3rd party options in the marketplace (pocket files for dropbox one of them), but since skydrive arguably became a better service since the last update and i have 25Gb, i made the switch and never looked back... Goodbye Dropbox, i was tired of waiting for you... Not Missing Dropbox
Pulse: There's one in the maketplace but its seriously lacking against ios version. laggy and somewhat basic features... i appreciate the effort in launching a wp7, but i kind of like its layout more in bigger screens (tablets) than smartphones. i may give it another try later... Weave its better imho, fast and i like its ui better for smartphones (lacks read it later support though, only instapaper)... Not missing Pulse
Pocket (read it later): they said they're looking into wp7, but idk... The best 3rd party client out there i believe to be "Read it at 7". its pretty good, but its not the real thing, articles are not perfectly formated as in the official pocket ios app... I do miss Pocket (RiL)
AutocadWS: nothing to say here... they said they may look into wp7 (i doubt it), and no 3rd party option in the market... I do miss AutocadWS
nba.tv: The gametime nba app just updated to support league pass, but for the US only. i have an international suscription and there's no option to use it in my phone. Android and iOS have nba.tv (international) apps... I miss badly an NBA.TV app
Photoshop express and others would be nice and all, but not really needed for me... i rather wp7 supported html5 streaming video, not just Youtube. in the ipad i could see almost any video out there in safari. In IE only youtube.