So many here say "it's illegal" without pointing to a single law. There is no such law to point to.
No municipality anywhere outlaws plugging in CE-approved appliances into your home's outlets. Even if half of them did, this would still be worthy of bringing up for the other half.
Even if it was illegal, wouldn't make such laws just or logical. Florida, after all, made off-grid living illegal. http://www.collective-evolution.com/2014/03/09/florida-makes...
Now what this approach _is_ is probably against the policies of your local electric utility, but they're incentivized to disallow anything that goes against their business interests, and can argue might somehow not be safe. Take for example HECO, Hawaii's electric utility, economically devastated by grid-tied PV.
http://khon2.com/2014/03/19/state-investigates-illegal-photo...
The way a grid-tie inverter works is like trying to jump on a merry go round that's already moving. In the happy path, the inverter keeps the PV power detached until it's ready to find its moment and sync it up to the grid. As soon as that grid signal goes away, the inverter is no longer capable of finding the signal to continue injecting current. The PV panel doesn't cause an explosion if it suddenly goes from 0% output to 100% output to 0%, so it's not exactly a big deal for a grid-tie inverter to perform this matching- it's in fact central to its functionality.
Whether the grid goes down, your breaker trips, or you unplug the 110v line cord yourself, these things all function the same- safe for anybody foolish or unfortunate enough to directly contact the inverter's output lines with their bare hands. These things don't hurt electricians, whether they have 5 safety interlocks (fundamental to any grid-tie design) or 2-3 additional ones sometimes proscribed by certain electrical codes.
"non-'net' meters" are getting to be few and far between, and utilities don't like older models because they require manual meter readers to go door-to-door. Naturally, you should be aware of what your specific electric situation is before getting into by trying one of these things out, but this is a weak argument against DIY grid-tie (much better arguments against exist).
An amazing number of people don't understand how electric meters work. If your grid-connected panel puts out 200W (call it 2 amps) and your apartment is pulling 3 amps total, the electric meter will spin at a rate proportional to 1 amp. It doesn't require any intelligence or fancy technology. If your apartment is pulling 1 amp net, the electric meter will not spin any faster than 1 amp, no matter how old it is. The only difference between new and old meters is whether a surplus of 1 amp is read as -1 amp or 0 amps.
On the off chance you're dumb enough to hook more unregistered PV capacity onto your property than your monthly use merits, utilities may assess fines or lockouts, but none will charge you for the excess generated as if it was consumed. Most are required by law to pay you for it (though an insultingly low rate).
Am also a bit alarmed by how many downvotes I got for the words "cheap chinese", as if that was a red flag for safety. Inverters of every kind, from respected brands in respectable configurations, have gotten _really_ cheap (the same model I installed 10 years ago now costs 1/10 what it cost 10 years ago). They're also almost invariably now made in China.
The fact is, even if your inverter is an incendiary device waiting to happen, you have a large number of built-in safety devices: a circuit breaker and hopefully enough common sense to keep the inverter away from flammable objects, and not to bury the inverter in a ratpile of shredded newspaper and gunpowder. I'd consider the cheap inverters far more likely to simply konk out far before their time than cause any kind of safety hazard. Circuit breakers save lives.
As a worthy counterexample, a faulty inverter (though probably a faulty inverter installation, considering the fire spread) caused this house fire: http://www.telegraph.co.uk/news/earth/energy/solarpower/1209...