I was with Online.net for about 2 weeks before I quit/canceled my server. If you need a review, here's my feedback thus far.
Products: Their entire range is not for sale to international clients. Out of the 14 different models, only 5-ish can be bought by international clients. The rest are all limited to French nationals and you can't fake being one
Server/Setup: This was smooth. I got an SC for 9.99 euro, it took about 20 minutes to delivery from time of payment. These servers don't include KVM but they do have a control panel that allows you to reload the OS, etc. The cons? Too many. At least for this 'SC' type. Their official choice of OS's is EXTREMELY LIMITED. That means you're effectively forced to use either from their choice or ask them to manually hook up a KVM for you. But if you ask them to hook up a manual KVM for you, you're in for a surprise (read below).
Network: If you're looking to transmit data within Europe, particularly locations close to France, you're good. Anywhere outside Europe, the performance is atrocious! Their network is TERRIBLE. Single threaded uploads (download test on a US server) were crawling between 1 and 5 mbit. With multiple threads, I was able to hit somewhere between 30 and 50 mbit to my US servers (I have them from Phoenix, Chicago, Washington).
Support: No support. I mean that, literally. I opted for self-managed during checkout and none of the tickets I've opened with them to date were ever answered. Not even tickets related to billing/admin issues. I opened a ticket asking when they expected to restock a certain server. This is before I knew that said server was not available to international clients (since they don't clarify this anywhere). This ticket went unanswered for 8 days before I closed it. I posted in their forums complaining about lack of response and some forum moderator replied stating this was not the norm and asked me to post the ticket number and he'd take a look. I did so, but no one ever replied.
A second incident was me requesting for manual KVM since they only have CentOS 6 as a choice on their reload panel. I needed CentOS 5. That ticket went unanswered for 3 days. A third ticket asking them why my account was limited to only 1 server (accounts can not have more than 1 server unless you open a ticket asking them to lift this limit). This ticket was unanswered for 2 days straight. I tried posting on their twitter too (@online_fr), but no reply there too. They often have people asking for support on their twitter which would indicate ticket support is next to non-existent. From what I can deduce, this is a one man show as I've only ever seen one guy making announcements etc (Arnaud).
Pros: Cheap pricing, easy order process, accepts Paypal.
Cons: No support, terrible network, most configs limited to french, lack of usability on a server without KVM since support never replies to KVM requests.
Too many cons make this provider practically unusable. Unless you're french, they won't give a crap about you as a client so if pricing is an advantage, every other disadvantage makes the pricing unattractive. I mean if your server is ever down requiring manual intervention, you can forget them helping.