You are right. As long as your cumulative UBTI is less than $1k, there are no negative tax consequences. And you get the joy of getting your K-1 each year and ignoring it.
In fact you can own a fair amount of NRGY and not hit the $1k UBTI trigger. The "common wisdom" number quoted in brokerage reports is the tax shield on NRGY is 80%. That means that in a regular account you would pay income tax on 20% of the distributions you receive in a year. For many MLPs, UBTI is very close (or actually equal to) your taxable income. In 2008 my taxable income was 18% of my NRGY distribution, and my UBTI was 17%. There was also a small amount of qualified dividends, so my total taxable amount would have been close to 20%, as the published tax shield numbers imply.
So using today's 8% yield on NRGY, and using the 20% common wisdom number for the taxable percentage, one could have $62,500 in NRGY held in an IRA, and expect to have $1k of UBTI (simple math: $62,500*.2*.08 = $1,000).
I never 'push the bounds', as UBTI can vary from year to year. For example, if NRGY increases the distribution in 2010 the amount of UBTI will increase. But if I had <$50k in NRGY in an IRA I would NOT worry about hitting the $1k level in 2010 from NRGY alone.
Every year I 'manage' my UBTI in my IRA to make sure I stay under $1k. If I come close one year, I will sell a high UBTI generating MLP to keep it under for the next year. It turns out to be very easy...several of my holdings generate negative UBTI, which can offset positive UBTI's. Given the mix of MLPs I own in my IRA, I would have to be a much richer man than I am before I came anywhere close to $1k.