You now have two chances per month to win £1m, and it isn't really gambling in that your money is safe and can be withdrawn any time. I've found that the several £k invested returns more than it did when I had PEPs of the same value. The prizes come in steady £50s but a couple of years ago there was one of £1k, and I'm still waiting on the biggie!
I have had premium bonds since the day they started. Never won anything, but I know people who have. Not lost anything really, except possibly some low bank interest rate, on the amount of bond's I hold, but the value is still there, when and if I cash them in, not like the lottery.
I have had £20,000 worth for the last ten years or so, they used to be quite good, at least matching the building society interest, sometimes exceeding it. But since they have increased the size of the maximum prize to one million (it used to be 250,000), the number of small prizes have dropped in numbers and I have noticed a significant drop in return. So much so, that I have decided to cash them in after the start of December. (there is a larger draw in December)
With the larger main prizes, they are no longer a steady investment and I would not advise buying a large amount, as the return from an ISA, or building society will probably be better, unless you are very lucky.
Out of interest, I have had one, one thousand pound prize and two, five hundreds, over the years. The most I have won in one year is £1450. But that was exceptional, this year £250 so far, which is dire.