I have had the 540 pretty much since launch and cant really fault it.
It has locked up a couple of times over this period and very occosionally it will freeze in use (click screen anywhere to click it into life again). Other than that, no probs.
I drive about 40k a year in 2 vehicles so transfer it between the two, hence having no wire for the traffic service is ideal.
I subscribe to the live services, mainly for the traffic and to be honest it is pretty good providing you use your common sense. IE, it will tell you about traffic in 100 miles and suggest a diversion.... by the time you reach that area the traffic may of gone etc. Find it far more accurate than the RDS traffic I used to use. In fact, when there has been traffic indicated ahead, the back of the queue has been that accurate you can see it moving on the tomtom as the traffic builds up!!
I dont use the speed cameras from TT...not accurate enough, I use the other popular ones

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I do have it set up like this though. I use the other database for cameras buut have set up the TT live cameras so I get warnings of the locations that have been inputted on that day...ie in a similar fashion to the road angel connected. So in theory I should get warnings of locations where mobile cameras have been seen that day. Works for me!
Steve