Does anyone have any experience or recommendations ?
Costs beyond that are lawyer's time for doing a trademark search and filing the paperwork. I used a lawyer (and ended up spending about $1,200 including filing fees), but you can also file it yourself if money is tight.
I think it's definitely worthwhile. The odds of having to make use of your trademark are low, but having the trademark is extremely valuable if someone comes out with a similar product or service with a similar name.
Once your business becomes mega profitable where the cost is peanuts...THEN you can go and get it registered.
For instance, Salesforce.com has the (R) going on: http://salesforce.com
Gmail is doing the (TM): http://mail.google.com
My rough intuition is that the bigger you are, the better slapping (TM) on works, even if you're registered. Both (R) and (TM) add credibility, but I think the (R) works better as deterrent to somewhat savvy competitors, whereas the (TM) might be more recognized by consumers. Most people know that TM is trademark, and don't know what (R) means.
If cost is an issue - you can file a single application in a couple of classes in your local country, then broaden it out when funds allow until you cover the main countries you plan to operate.
At the company I work for at the moment, we filed globally from very early on (probably cost £100k or something and takes a year or so), but every time we have an issue with a fraudulent domain name registration or something, we can recover it in days.
Plus you can capitalise this as an asset, it's not an expense, so there are no downsides to it.
I can recommend a specialist firm like Williams Powell (http://www.williamspowell.com) in the UK.
Have you needed to recover a squatted domain? Have you had success with it, due to your TM? (Although I've never been in the situation,) I've heard it's tough to recover in either situation -- was your experience better b/c of the TM?
My one recommendation is that if you are cost conscious, send your IP projects (copyright, patent, trademark) to a boutique or, as we call them, a 'mill'. Having worked in both boutique and large conglomerate firm settings, I can attest to the fact boutiques are far more organized and, because their overhead is so much less, far less expensive.
W/r/t at what point in your development cycle you should register the TM, I have seen the spectrum of very early to very late filings. While in one instance a late-stage filing resulted in more similar marks out there (and the class claims for goods/ services had to be much more limited) I have not yet seen it be detrimental to getting registered eventually.
On the other hand, small start-ups (both net based and brick-and-mortar) account for a disproporionate number of the applications we have to let go abandoned due to client request or nonpayment.