I've been using Bloglines for quite a while to subscibe to web feeds, and it has worked wonderfully even with over 1000 subscriptions. Looking around about 18 months ago, nothing else seemed to deal well with that number of feeds.
Google Reader though, has developed and looks like a possible competitor. So in this post I'll take a quick look at how the two compare.
With both services the experience of browsing feeds, marking them as read, and following links is fine. There is no major difference between the two.
Subscribing to feeds is simple in both, but while Bloglines makes it easy to choose what folder the feed with be held in, Google requires you to choose it manually. A small point, but it's an extra step.
With Bloglines I used Yahoo Pipes to translate the feed's contents into English, which takes 10 minutes to set up, but Google reader allows you to set a feed to be translated into your language by going to 'Folder settings' and choosing 'Translate into my language'. This is much easier.
If you use lots of Google's applications, Google Reader would integrate well with them, and save you logging into an extra service. If you like stats, Google Reader keeps track of which feeds you are reading posts from, amoung other things. Bloglines still makes it easier than Google Reader to manage large numbers of feeds, and folders.
Overall there isn't a major difference between the two services. Because it is easy to try different feed readers, by exporting your OPML file and importing it into another service, it's easy to give both a go and discover which works best for you.