Fact: Polish people can claim CHB as soon as they come here. It's the only benefit you can get straight away.
Child tax credit - Im not sure if it's so simple as it depends on your income.
However, last year or begining of this year I read soemwhere that CHB will be given only to children who live here. I think that is very fair and reasonable approach. IF it happens.
Other benefits
I also thought that one of the conditions to be able to claim other benefits (housing, council tax tec) was to be 'in a continous employment for 12 months' however, I've been proved wrong recently.
Apparently one can claim any sort of benefits as soon as they take up an employment and stay in it, without the requirement of 12 mth continous employment. If that's the case, the whole Work Registration Scheme doesn't make sense.
Original statement 2004 re: EU nationals and benefits:
press.homeoffice.gov.uk/press-releases/No_Uk_Benefits_For_Eu_Accession_
How it evolved and what is happening now:
There is a common myth that A8 nationals on the WRS do not have housing or benefit rights until they have worked for 12 months. This is simply untrue.
housing-rights.info/02_7_A8_nationals.html
Fact - all benefits in Poland have been, and I believe they still are, means tested. It's not the case in the UK.
Fact - NHS is free in the UK
Fact - a friend of mine, who happens to be working in Poland on and off since 1997, had a problem with accessing Polish health care system. I went to a local doctor with him once. He was refused to be treated under the 'national healthcare system' and adviced to see a doctor privately. It was way back in late 1990 - and I know that back then Poland had an agreement with UK re: accessing the national healthcare system which allowed Polish people to access NHS for free (before 2004) and the same supposed to be happening in Poland - any UK national should be treated without problem for free. It wasn't the case.
I also visited Poland last year and required a medical attention. Ended up in a hospital's A&E in the middle of the night and was flatly refused help because...I don't pay Polish ZUS. Thank God for a cousin-doctor. It wouldn't happen to a Polish person here, in the UK.
So if you ask me, yes, UK is very lenient - and way too leninet and easy. That's why Polish people (and not only) come here.